Fungal infections are killing sea fans (Gorgonia spp.) all over the Caribbean, with grave consequences for health of coral reefs. These infections are aspergillosis--that is, the pathogen is Aspergillus--and in some ways they resemble aspergillosis in humans. Various causes of sea fan aspergillosis have been proposed: spores in dust clouds from the Sahara nutrient deposition from Sahara dust clouds, terrestrial runoff, and environmental stress. All published studies have focused on the fungus A. sydowii as the sole pathogen. However, preliminary data from Puerto Rico suggest that at least four species of Aspergillus infect sea fans, some of which are known to produce mycotoxins. The long-term goal of this project is to be able to predict and prevent aspergillosis in sea fans, and to understand common mechanisms of aspergillosis in human and sea fan infections. This project includes four key steps towards this goal: 1) determine which species of Aspergillus infect sea fans in Puerto Rico, by isolation of fungi and DNA sequencing; 2) determine if Aspergillus isolated from sea fans are pathogenic by fulfiilling Koch's postulates, using sea fans in aquarium tanks; 3) test the role of stress in susceptibility of sea fans to aspergillosis, by testing for presence of heatshock proteins; and 4) determine if the strains of Aspergillus isolated from sea fans produce mycotoxins in vitro, since mycotoxins contribute to pathogenicity in fungal infections of humans. The overall hypothesis is that various species of Aspergillus cause aspergillosis, that the pathogens are opportunistic, and that mycotoxins and environmental stress contribute to the disease. Understanding the causal agents, physiological responses and environmental factors that contribute to the disease are crucial steps towards prevention.